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Tropical Storm Teddy Forecast Discussion Number 12
2020-09-15 16:34:30| National Hurricane Center (Atlantic)
Issued at 1100 AM AST Tue Sep 15 2020 000 WTNT45 KNHC 151434 TCDAT5 Tropical Storm Teddy Discussion Number 12 NWS National Hurricane Center Miami FL AL202020 1100 AM AST Tue Sep 15 2020 Teddy's structure is slowly improving. Visible and IR imagery indicate that inner-core convection has increased, despite the continued presence of dry slots. The latest Dvorak intensity estimates from TAFB and SAB support the initial intensity of 55 kt. Teddy is still heading west-northwestward for the moment with a forward speed estimate of 11 kt. Teddy will likely turn northwestward today and continue steadily moving northwestward along the southwest periphery of a ridge over the central Atlantic for the next several days. In fact, all available guidance indicates that once it makes that northwestward turn, Teddy will barely deviate from its heading or forward speed for the rest of the week. The latest NHC track forecast is virtually identical to the previous one. The model spread is smaller than usual and confidence in the track forecast is high. Teddy's low shear and warm SST environment should be conducive for further strengthening, and the NHC intensity forecast is largely unchanged. Some dry air in the environment could restrict Teddy's intensification rate, but is not expected to prevent Teddy from becoming a hurricane later today or tonight. Continued strengthening is expected thereafter and Teddy is forecast to become a major hurricane within the next few days. On the whole, the intensity guidance is a little lower at the longer-range times, so the NHC forecast at days 4 and 5 is at the very top end of the guidance. I'd rather see a more consistent signal from the models before making a larger change to the forecast, especially given the impressive depiction of Teddy in the global model forecasts at that time. The 34 kt wind radii were expanded to the northwest of Teddy based on data from an 1136 UTC ASCAT-A overpass. FORECAST POSITIONS AND MAX WINDS INIT 15/1500Z 14.0N 47.0W 55 KT 65 MPH 12H 16/0000Z 14.9N 48.2W 65 KT 75 MPH 24H 16/1200Z 16.1N 49.5W 75 KT 85 MPH 36H 17/0000Z 17.4N 50.8W 85 KT 100 MPH 48H 17/1200Z 18.9N 52.3W 95 KT 110 MPH 60H 18/0000Z 20.3N 53.6W 100 KT 115 MPH 72H 18/1200Z 21.5N 55.0W 105 KT 120 MPH 96H 19/1200Z 24.0N 57.4W 110 KT 125 MPH 120H 20/1200Z 27.1N 60.0W 100 KT 115 MPH $$ Forecaster Zelinsky
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Tropical Storm Karina Forecast Discussion Number 11
2020-09-15 16:33:35| National Hurricane Center (East Pacific)
Issued at 800 AM PDT Tue Sep 15 2020 000 WTPZ41 KNHC 151433 TCDEP1 Tropical Storm Karina Discussion Number 11 NWS National Hurricane Center Miami FL EP162020 800 AM PDT Tue Sep 15 2020 Karina has changed little in organization over the past several hours with a concentrated area of deep convection mostly over the southwestern portion of the circulation and over the estimated position of the low-level center. The initial intensity is kept at 50 kt based on a blend of the latest Dvorak CI numbers from TAFB and SAB and the objective UW-CIMSS ADT. Karina is now crossing the 26 isotherm, so it is unlikely that any further strengthening will occur. The cyclone is forecast to move over progressively cooler waters and into a drier, more stable atmosphere over the next couple of days. These conditions should induce a weakening trend soon, and the deep convection is expected to gradually wane during that time. Karina is forecast to become a convection-free remnant low by 60 h, or perhaps a little sooner. The latest NHC intensity forecast is in good agreement with the various guidance aids. The initial motion of the tropical storm is 310/09 kt, as it continues to move along the periphery of a mid-level ridge to its northeast. This general motion should continue while the system maintains convection. As the system becomes devoid of convection, a turn to the west and west-southwest is anticipated as the cyclone moves within the low-level flow. FORECAST POSITIONS AND MAX WINDS INIT 15/1500Z 20.4N 121.1W 50 KT 60 MPH 12H 16/0000Z 21.3N 122.2W 45 KT 50 MPH 24H 16/1200Z 22.4N 123.9W 40 KT 45 MPH 36H 17/0000Z 23.3N 125.2W 35 KT 40 MPH 48H 17/1200Z 23.7N 126.2W 30 KT 35 MPH 60H 18/0000Z 23.9N 127.3W 25 KT 30 MPH...POST-TROP/REMNT LOW 72H 18/1200Z 23.5N 128.3W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 19/1200Z 22.6N 130.7W 20 KT 25 MPH...POST-TROP/REMNT LOW 120H 20/1200Z...DISSIPATED $$ Forecaster Latto
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Hurricane Sally Forecast Discussion Number 16
2020-09-15 11:15:29| National Hurricane Center (Atlantic)
Issued at 400 AM CDT Tue Sep 15 2020 000 WTNT44 KNHC 150914 CCB TCDAT4 Hurricane Sally Discussion Number 16...Corrected NWS National Hurricane Center Miami FL AL192020 400 AM CDT Tue Sep 15 2020 Corrected Key Messages 2 and 3 There has been little change overall in Sally's convective structure in both satellite and Doppler radar data. An eye has tried to close off several times this morning, but after less than 30 minutes the southern eyewall has eroded. Until just recently, the central pressure had been steady for the past several hours at 986 mb. However, the most recent Air Force Reserve reconnaissance pass through Sally's center reported a dropsonde pressure of 984 mb and 13 kt winds, which equals a pressure of 983 mb. Maximum 700-mb flight-level winds observed have only been 63 kt and peak SFMR winds have been 58 kt. Also, reports from nearby oil rigs have dropped off significantly since yesterday are are now in the 40-50 kt range. Based on these data, the initial intensity has been lowered to 75 kt. The initial motion estimate to 300/02 kt. After a brief jog due west, it appears that Sally has resumed a slow drift toward the west-northwest. Sally is embedded within weak steering flow based on 0000Z upper-air data indicating 500-mb heights of 5900 meters and slightly higher surrounding the cyclone from Florida northward into the Tennessee Valley and then westward into the central and southern Plains. This weak steering pattern is expected to persist for the next few days, with a weak mid-level trough forecast to move into the Missouri and Tennessee Valleys by Wednesday and Thursday, which will gradually lift Sally northward and then northeastward. Sally is forecast to merge with a frontal system by day 4 or 5. The new NHC forecast track is similar to the previous advisory and lies down the middle of the rather divergent model guidance envelope. Sally is now expected to remain in a moderate to high mid-to upper-level wind shear environment. Ina addition, some modest upwelling is likely occurring in the inner-core region based a SST decrease of nearly 2 deg F during the past 24 hours based on data from buoy 42012. After the Sally makes landfall, rapid weakening is forecast and Sally should become post-tropical in 3 days or less. Users are reminded to not focus on the exact forecast track or the specific timing and location of landfall. Hurricane-force winds, dangerous storm surge, and flooding rainfall will affect a large portion of the north-central Gulf Coast during the next few days. KEY MESSAGES: 1. It is still too early to determine where Sally's center will move onshore given the uncertainty in the timing and location of Sally's northward turn near the central Gulf Coast. Users should not focus on the details of the official forecast track, since NHC's average forecast error at 36 hours is around 60 miles, and dangerous storm surge, rainfall, and wind hazards will extend well away from the center. 2. An extremely dangerous and life-threatening storm surge is expected for areas outside the southeastern Louisiana Hurricane and Storm Damage Risk Reduction System from the Mouth of the Mississippi River to the Okaloosa/Walton County Line in the Florida Panhandle, where a Storm Surge Warning is in effect. Residents in these areas should follow any advice given by local officials. 3. Hurricane conditions are expected today within the Hurricane Warning area along the Mississippi and Alabama coastlines and the western Florida Panhandle. Tropical storm conditions are already occurring in some of these areas. 4. Historic flooding is possible with extreme life-threatening flash flooding likely through Wednesday along and just inland of the central Gulf Coast from the western Florida Panhandle to far southeastern Mississippi. Widespread moderate to major flooding on area rivers is forecast along and just inland of the central Gulf Coast. Significant flash and urban flooding, as well as widespread minor to moderate river flooding is likely across inland portions of Mississippi, Alabama, northern Georgia, and the western Carolinas through the week. FORECAST POSITIONS AND MAX WINDS INIT 15/0900Z 28.9N 88.1W 75 KT 85 MPH 12H 15/1800Z 29.2N 88.4W 75 KT 85 MPH 24H 16/0600Z 29.9N 88.5W 75 KT 85 MPH 36H 16/1800Z 30.6N 88.3W 60 KT 70 MPH...INLAND 48H 17/0600Z 31.4N 87.5W 35 KT 40 MPH...INLAND 60H 17/1800Z 32.2N 86.2W 25 KT 30 MPH...INLAND 72H 18/0600Z 32.8N 84.6W 20 KT 25 MPH...POST-TROP/REMNT LOW 96H 19/0600Z 33.2N 81.3W 20 KT 25 MPH...POST-TROP/EXTRATROP 120H 20/0600Z...DISSIPATED $$ Forecaster Stewart
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Hurricane Sally Forecast Discussion Number 16
2020-09-15 11:05:59| National Hurricane Center (Atlantic)
Issued at 400 AM CDT Tue Sep 15 2020 000 WTNT44 KNHC 150905 CCA TCDAT4 Hurricane Sally Discussion Number 16...Corrected NWS National Hurricane Center Miami FL AL192020 400 AM CDT Tue Sep 15 2020 Corrected initial intensity from 80 kt to 75 kt There has been little change overall in Sally's convective structure in both satellite and Doppler radar data. An eye has tried to close off several times this morning, but after less than 30 minutes the southern eyewall has eroded. Until just recently, the central pressure had been steady for the past several hours at 986 mb. However, the most recent Air Force Reserve reconnaissance pass through Sally's center reported a dropsonde pressure of 984 mb and 13 kt winds, which equals a pressure of 983 mb. Maximum 700-mb flight-level winds observed have only been 63 kt and peak SFMR winds have been 58 kt. Also, reports from nearby oil rigs have dropped off significantly since yesterday are are now in the 40-50 kt range. Based on these data, the initial intensity has been lowered to 75 kt. The initial motion estimate to 300/02 kt. After a brief jog due west, it appears that Sally ahs resumed a slow drift toward the west-northwest. Sally is embedded within weak steering flow based on 0000Z upper-air data indicating 500-mb heights of 5900 meters and slightly higher surrounding the cyclone from Florida northward into the Tennessee Valley and then westward into the central and southern Plains. This weak steering pattern is expected to persist for the next few days, with a weak mid-level trough expected to move into the Missouri and Tennessee Valleys by Wednesday and Thursday, which will gradually lift Sally northward and then northeastward. Sally is forecast to merge with a frontal system by day 4 or 5. The new NHC forecast track is similar to the previous advisory and lies down the middle of the rather divergent model guidance envelope. Sally is now expected to remain in a moderate to high mid-to upper-level wind shear environment. Ina addition, some modest upwelling is likely occurring in the inner-core region based a SST decrease of nearly 2 deg F during the past 24 hours based on data from buoy 42012. After the Sally makes landfall, rapid weakening is forecast and Sally should become post-tropical in 3 days or less. Users are reminded to not focus on the exact forecast track or the specific timing and location of landfall. Hurricane-force winds, dangerous storm surge, and flooding rainfall will affect a large portion of the north-central Gulf Coast during the next few days. KEY MESSAGES: 1. It is still too early to determine where Sally's center will move onshore given the uncertainty in the timing and location of Sally's northward turn near the central Gulf Coast. Users should not focus on the details of the official forecast track, since NHC's average forecast error at 36 hours is around 60 miles, and dangerous storm surge, rainfall, and wind hazards will extend well away from the center. 2. An extremely dangerous and life-threatening storm surge is expected for areas outside the southeastern Louisiana Hurricane and Storm Damage Risk Reduction System from Port Fourchon, Louisiana, to the Okaloosa/Walton County Line in the Florida Panhandle, where a Storm Surge Warning is in effect. Residents in these areas should follow any advice given by local officials. 3. Hurricane conditions are expected early Tuesday within the Hurricane Warning area in southeastern Louisiana and are expected by late Tuesday and Tuesday night within the Hurricane Warning area along the Mississippi and Alabama coastlines and the western Florida Panhandle. Tropical storm conditions are already occurring in some of these areas. 4. Historic flooding is possible with extreme life-threatening flash flooding likely through Wednesday along and just inland of the central Gulf Coast from the western Florida Panhandle to far southeastern Mississippi. Widespread moderate to major flooding on area rivers is forecast along and just inland of the central Gulf Coast. Significant flash and urban flooding, as well as widespread minor to moderate river flooding is likely across inland portions of Mississippi, Alabama, northern Georgia, and the western Carolinas through the week. FORECAST POSITIONS AND MAX WINDS INIT 15/0900Z 28.9N 88.1W 75 KT 85 MPH 12H 15/1800Z 29.2N 88.4W 75 KT 85 MPH 24H 16/0600Z 29.9N 88.5W 75 KT 85 MPH 36H 16/1800Z 30.6N 88.3W 60 KT 70 MPH...INLAND 48H 17/0600Z 31.4N 87.5W 35 KT 40 MPH...INLAND 60H 17/1800Z 32.2N 86.2W 25 KT 30 MPH...INLAND 72H 18/0600Z 32.8N 84.6W 20 KT 25 MPH...POST-TROP/REMNT LOW 96H 19/0600Z 33.2N 81.3W 20 KT 25 MPH...POST-TROP/EXTRATROP 120H 20/0600Z...DISSIPATED $$ Forecaster Stewart
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Tropical Storm Teddy Forecast Discussion Number 11
2020-09-15 10:57:26| National Hurricane Center (Atlantic)
Issued at 500 AM AST Tue Sep 15 2020 000 WTNT45 KNHC 150857 TCDAT5 Tropical Storm Teddy Discussion Number 11 NWS National Hurricane Center Miami FL AL202020 500 AM AST Tue Sep 15 2020 The tropical storm appears to have gotten better organized overnight, with deeper convection near the center and an increase in banding features. The initial wind speed is nudged upward to 50 kt, a little lower than the subjective Dvorak estimates alone would indicate since they have been running a little hot for this storm. While there are no signs of a true inner core yet, the shear is quite low at present, and Teddy should have several days in a low or moderate shear environment over warm waters to strengthen. Thus, the new forecast is raised from the previous one and is closest to a blend of the Florida State Superensemble and the NOAA corrected- consensus guidance. Teddy bears watching in the long range for category 4 strength, but regardless of the details, all of the guidance show it becoming a classical large and powerful September hurricane. The storm has turned west-northwestward tonight, or 295/10 kt. Teddy remains in a well-defined steering current for the next several days on the southwestern edge of the central Atlantic ridge, causing a west-northwest to northwest track through the end of the forecast. While the guidance is in very good agreement, there's been a rightward shift of almost all the aids, perhaps due to more upper-level westerly flow than the last cycle. The NHC track forecast is shifted eastward but lies on the western side of the guidance envelope. FORECAST POSITIONS AND MAX WINDS INIT 15/0900Z 13.7N 46.0W 50 KT 60 MPH 12H 15/1800Z 14.4N 47.2W 60 KT 70 MPH 24H 16/0600Z 15.6N 48.7W 75 KT 85 MPH 36H 16/1800Z 16.8N 50.0W 85 KT 100 MPH 48H 17/0600Z 18.2N 51.5W 90 KT 105 MPH 60H 17/1800Z 19.7N 52.9W 100 KT 115 MPH 72H 18/0600Z 21.0N 54.2W 105 KT 120 MPH 96H 19/0600Z 23.5N 56.8W 110 KT 125 MPH 120H 20/0600Z 26.5N 59.5W 105 KT 120 MPH $$ Forecaster Blake
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